Many electrical devices are currently run with the use of layered electrical storage devices, such as integrated circuit chips and printed circuit boards. However, when the outside electrical source to these devices is disrupted, the operation of these devices ceases. Needless to say, is usually detrimental the entire purpose for operating the device.
A typical example is the modern digital alarm clock. Presently, most alarm clocks are run by a household current. A printed circuit board containing integrated circuit chips usually drives all the functions of the clock, including keeping track of the time and the alarm times. When there is a disruption of the current to the alarm clock, all this information is lost. The current time, the time the alarm is set for, and numerous other pieces of information are lost even during the minutest disruption in the normal power supply. It is not good to awaken in the morning to a blinking alarm clock that has not gone off at the proper time due to a minor power outage during the evening or early morning hours.
In addition to a compete power failure, these problems occur when a "brown-out" situation occurs. The main power to an appliance falls beneath a critical threshold at which the appliance operates in a predictable manner. In addition, "brown out" situations can actually harm the electronic components in these devices.
It is necessary that alternate electrical power be supplied to the critical functions of these devices. By supplying backup power to loads requiring electrical energy for continued operation, operational loads of the electric appliance or device, predictable operation for the electrical device is ensured. Further, damage to operational loads is decreased when an alternate power supply is available.
A solution to this problem is to buy a dedicated backup power supply. Such power supplies are common for critical electrical devices, including computers. However, the size and complexity of backup power supplies makes these devices impracticable for common household electronics consuming low amounts of electrical energy, such as an alarm clock.
Another solution is to add a common electrochemical battery to the appliance. However, the electrochemical backup battery adds a great deal of space and volume to any electrical appliance and is usually not worth the space expended. What is needed is a compact, easily manufactured, energy storage device for detecting a loss or drop of a power supply potential and maintaining critical functions of an electrical device during such a loss or drop of power supply potential.
It is desirable that any backup power supply be contained within or integral to a layered electrical device within a piece of common electronic equipment. Modularity and ease of manufacture dictate that a backup power supply be small enough to fit in the texture of any small electronic device. Thus, as stated before, many common backup electric power supplies cannot be utilized. Further, it is advantageous to put the backup power supply within or integral to the board or chip rather than connect it as a discrete component for several reasons. This backup power supply should be an electric storage device, or an electric energy source, embedded in the fabric of the electric device.
Usually, the volume consumed by a layered electrical device or assembly, such as a printed circuit board, or integrated circuit chip, is a very valuable commodity in the design of an electronic assembly device. The volume of the assembly dictates the number, size, and placement of components on it. In addition, with the advent of personal computers, a major limitation is in the space available for components to exist above the actual device surface. For example, minimization of the space used above the actual device represents a minimization of volume used for a system of printed circuit boards connected to a common bus, and thus maximizing the use for that volume.
The area of a surface consumed by mounted devices on a circuit board is also a very valuable commodity. Therefore, to reduce the surface area used by a mounted device lets the designer use that much more surface area for additional functional devices. Specifically, if one could redesign a circuit board with all the electric storage devices embedded within the board, a designer could use much more surface area for additional functional devices on that circuit board. Or, the designer could reduce the entire assembly size.
Similarly, if an integrated circuit chip (IC chip) could embed smaller, more powerful electric storage devices within the layers making up the chip, more volume of the chip could be dedicated to other functional purposes.
Typically, in a printed circuit board, the design of the circuitry requires some sort of energy storage device, such as a capacitor or battery. The designer usually chooses a discrete component for such a storage device in the circuit. This discrete component occupies surface area of the board and an amount of volume in and above the board.
During the printed circuit board manufacturing process, the spot where the energy storage device is to be placed is left blank for attachment later. Usually, a manufacturer manufactures the circuit board with holes placed where the leads of the storage device will be attached. Later, a discrete electrical storage device, such as a battery or capacitor, is placed into the circuit and electrically attached to the circuit board with a secondary interconnection such as a screw on contact or soldered joint. Usually, the circuit connections are terminated at the hole where the storage device leads will be placed, and when the storage device leads are guided into the hole, this completes the circuit path.
However, using discrete electrical storage device components has several drawbacks. One main drawback is that most of the electrical storage device components and the necessities for their connection to the circuit take up valuable surface area on and occupy volume in and above the board.
With respect to IC chips, large electrical storage devices are impracticable. First, an IC chip usually does not have any interconnections to discrete devices through its surface. Second, the small volume of a chip does not lend itself to large or medium electrical storage devices.
Generally, energy storage devices in particular require large areas and volumes, and tend to tower above other components on a board. Even smaller energy storage devices on a circuit board can be the tallest components on a board. These devices present design problems due to placement, and take up valuable board surface area and volume.
The equation (k.times.A)/T defines the capacitance of an energy storage device, or a measure of the amount of electric charge it can hold. In the equation, k stands for the dielectric constant of the material between two opposite charged plates, A being the area of the smallest plate, and T being the thickness of the dielectric material. Thus, small volumes and areas, without a high dielectric constant, make smaller capacitances. For very small volumes and areas, such as in an IC chip, large storage devices are impracticable due to space limitations and the fact that most IC chips do not provide for a surface interconnection to other discrete components.
If a design requires a larger energy storage device in a particular, the problem is amplified further. A larger storage device tends to require a larger area and volume to house the discrete component. Usually, for printed circuit boards, the solution is to place the capacitors where they extend outward from the board.
An example of the space needed for energy storage can be shown in the context of a power supply, where the functional components can take up about 30% of a board's space. A need exists for backup electric energy storage devices contained in the fabric of the layered electrical device. This backup electric storage device would go on when power is cut to the layered electrical device to make sure that during a minor power cut, no information is lost in that brief moment. A discrete interconnected storage device for common appliances, such as a modern digital alarm clock, is impracticable due to space and cost limitations.
Further, several problems exists when a discrete storage device must be interconnected into the circuit board. Usually, a manufacturer must solder all components into a connection to the circuit in the printed circuit board. This interconnection is a weak point and the cause of many failures in printed circuit board packages. The interconnection is also a point where manufacturing mistakes can occur. Thus, an energy storage device integrated directly into the layers of a layered electrical device, such as a printed circuit board or IC chip, is very valuable. If the energy storage device is integral to the the layered electrical device, that is formed as part of the layered electrical device and not added in later stages, this improves the reliability of the device and is therefore beneficial to overall performance.
In an integrated circuit chip, the spaces involved are so small that significant energy storage is not possible. The only place to put any energy storage device is in the substrate comprising the integrated circuit chip. Thus significant energy storage, as a battery or capacitor, is untenable for these devices.
What is needed is an apparatus in which the energy storage device components do not take up area on the surface of and volume above a layered electrical device. If this could be achieved, this would free up valuable area for the placement of components and free up the volume used by discrete components. In addition, an integrated electrical energy storage device formed in the substrates of an IC chip could greatly enhance the functionality of that chip. Further, an integrated energy storage device in a layered electrical device is needed to enhance semiconductor performance, since it eliminates some soldered connections. Further, the energy storage device must provide the functionality of switching on its stored electrical energy when the normal power supply has been cut off.